Sources of variation in simulated ecosystem carbon storage capacity from the 5th Climate Model Intercomparison Project (CMIP5)

Ecosystem carbon (C) storage strongly regulates climate-C cycle feedback and is largely determined by both C residence time and C input from net primary productivity (NPP). However, spatial patterns of ecosystem C storage and its variation have not been well quantified in earth system models (ESMs), which is essential to predict future climate change and guide model development. We intended to evaluate spatial patterns of ecosystem C storage capacity simulated by ESMs as part of the 5th Climate Model Intercomparison Project (CMIP5) and explore the sources of multi-model variation from mean residence time (MRT) and/or C inputs. Five ESMs were evaluated, including C inputs (NPP and [gross primary productivity] GPP), outputs (autotrophic/heterotrophic respiration) and pools (vegetation, litter and soil C). ESMs reasonably simulated the NPP and NPP/GPP ratio compared with Moderate Resolution Imaging Spectroradiometer (MODIS) estimates except NorESM. However, all of the models significantly underestimated ecosystem MRT, resulting in underestimation of ecosystem C storage capacity. CCSM predicted the lowest ecosystem C storage capacity (~10 kg C m−2) with the lowest MRT values (14 yr), while MIROC-ESM estimated the highest ecosystem C storage capacity (~36 kg C m−2) with the longest MRT (44 yr). Ecosystem C storage capacity varied considerably among models, with larger variation at high latitudes and in Australia, mainly resulting from the differences in the MRTs across models. Our results indicate that additional research is needed to improve post-photosynthesis C-cycle modelling, especially at high latitudes, so that ecosystem C residence time and storage capacity can be appropriately simulated

Response of the soil microbial community composition and biomass to a short-term Spartina alterniflora invasion in a coastal wetland of eastern China

Plant invasion has been reported to alter ecosystem carbon (C) and nitrogen (N) cycling processes and pools. The mechanisms involved in how plant invasion affects the soil microbial community-the primary mediator of soil C and N cycling-remain poorly understood. The objective of this study was therefore to evaluate the effect of plant invasion on the soil microbial community in a coastal wetland of eastern China. We investigated the impact of an exotic C-4 perennial grass, Spartina alterniflora, on the soil microbial community structure based on phospholipid fatty acids (PLFAs) analysis and chloroform fumigation-extraction by comparing it to that of bare flat and native C-3 plants Suaeda salsa and Phragmites australis communities. Spartina alterniflora invasion significantly increased soil microbial biomass C and the total and various types of PLFAs compared with bare flat, Suaeda salsa and Phragmites australis communities. Increased concentrations of soil moisture, electrical conductivity, water-soluble organic carbon (WSOC), and total, labile and recalcitrant soil organic C and N, and decreased soil pH in Spartina alterniflora community explained 65.9 % of the total variability in the PLFAs. WSOC and soil labile organic N were strongly correlated with PLFAs, whereas soil pH was negatively related to PLFAs. A 10-year Spartina alterniflora invasion significantly altered soil microbial biomass and community structure by increasing available substrate. The changes in soil microbial biomass and community structure may in turn enhance soil C and N sequestration in a coastal wetland of eastern China

The effect of microbial inoculant origin on the rhizosphere bacterial community composition and plant growth-promotion

Microbial inoculation has been proposed as a potential approach for rhizosphere engineering. However, it is still unclear to what extent successful plant growth-promoting effects are driven by the origin of the microbial inocula and which taxa are responsible for the plant-beneficial effects